1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) is a high explosive of great brisance, which is usually produced according to the Bachmann process and variations there of by nitrolysis of hexamethylenetretramine (hexamine) with a solution of ammonium nitrate in concentrated nitric acid in the presence of acetic anhydride according to the following overall equation: EQU C.sub.6 H.sub.12 N.sub.4 + 4HNO.sub.3 + 2NH.sub.4 NO.sub.3 + 6(CH.sub.3 CO).sub.2 O.fwdarw. 2 C.sub.3 H.sub.6 O.sub.6 N.sub.6 + 12 CH.sub.3 COOH
the reagents are preferably employed in excess over the stoichiometric proportions of nitric acid, ammonium nitrate and acetic anhydride, and are usually added incrementally to a reactor charged with a heel consisting essentially of acetic acid, which may contain up to a few percent of nitric acid, ammonium nitrate and acetic anhydride.
The nitrolysis of hexamine to RDX according to the Bachmann process yields a slurry of RDX in anhydrous spent acid. Normally, the anhydrous slurry is diluted with water to about 40% water content and simmered to destroy undesirable by-products, notably linear nitramines. The slurry is then cooled and filtered to separate the crude RDX from the spent acid (filtrate). At this point the spent acid contains about 40% water, along with acetic acid, nitric acid, and ammonium nitrate, together with various small amounts of RDX and HMX (1,3,5,7-tetranitro- 1,3,5,7-tetraazacyclooctane) and other constituents. The process, as industrially practiced, requires that the total volume of dilute spent acid be processed through the complete recovery system, including costly distillation and other operations, to be reconstituted to acetic acid and acetic anhydride prior to reuse in the manufacture of RDX.